Examples of an image display device include a liquid crystal display device. The liquid crystal display device includes a liquid crystal panel as a spatial modulation element and a light-emitting device (backlight) that emits light toward a back surface of the liquid crystal panel. By spatially modulating light passing through the liquid crystal panel, an image is formed on the liquid crystal panel.
In order to further enhance the presence of the image displayed on the liquid crystal display device, a 3D liquid crystal display device capable of displaying a 3D (three-dimensional) image has been developed. This 3D liquid crystal display device can present different images to viewer's left and right eyes to produce parallax, thereby causing the viewer to visually recognize a 3D image.
For example, there has been proposed a glasses-type 3D liquid crystal display device in which the viewer puts on dedicated glasses having a special optical effect to visually recognize the 3D image. However, in this glasses-type 3D liquid crystal display device, the viewer must take the trouble of putting on the glasses, which is inconvenient. For this reason, in recent years, a glasses-free 3D liquid crystal display device that enables the viewer to visually recognize the 3D image with his/her naked eyes has been proposed (Refer to, for example, Patent literature 1).
In a light-emitting device of the glasses-free 3D liquid crystal display device, for example, a right light source and a left light source are disposed on both respective side surfaces of a light guide plate having special shape. The right light source and the left light source are alternately lighted. When the right light source is lighted, light from the right light source is incident on one side surface of the light guide plate, and light emitted from the light guide plate is focused on the right eye of the viewer. When the left light source is lighted, light from the left light source is incident on the other side surface of the light guide plate, and light emitted from the light guide plate is focused on the left eye of the viewer. By displaying an image for right eye on the liquid crystal panel while the right light source is lighted and displaying an image for left eye while the left light source is lighted, the viewer can visually recognize the 3D image with his/her naked eyes. This principle can be applied to the 3D liquid crystal display device as well as a privacy display that prevents the third person from peeping the displayed image.